1. Field of the Invention
The present invention relates to a thin type display device thin type display device which is made its display portion a thin type by various methods such as a liquid crystal method, a plasma method, a rear projection method or the like, in particular, the present invention relates to a thin type display device which is provided with a rotation driving mechanism (swivel mechanism) to make the display portion rotate in horizontal direction.
2. Description of the Related Art
Conventionally, there is a display device which is provided with a rotation driving mechanism (swivel mechanism) to rotate a display portion by transmitting rotating force of a motor in order to rotate the display portion on which an image is displayed to reproduce in horizontal direction. As for such rotation driving mechanism, not only mechanism that is formed for a display device in which the display portion is composed of a Braun tube (See, JP-UM-A-S63-124775, JP-UM-A-H03-042186, JP-A-H04-061575), but recently mechanism that is formed for a thin type display device in which the display portion is made a thin type by various methods such as a liquid crystal method, a plasma method, a rear projection method, or the like (See, JP-A-2004-304679), is also proposed.
According to the rotation driving mechanism that is disclosed in JP-UM-A-H03-042186, it has a structure in that an electromagnetic clutch is controlled in response to magnitude of loaded electric current when a driving motor is operated in order that stopping of rotating operation or appropriate control can be performed if the display portion collides with an obstruction when it is rotating. That is, because the loaded electric current of the driving motor becomes large when the display portion collides with the obstruction, the mechanism detects the collision with the obstruction based on the loaded electric current, and rotation of the display portion is stopped by cut off of the electromagnetic clutch.
Further, according to the rotation driving mechanism that is disclosed in JP-A-H04-061575, it has a structure in that the rotation driving mechanism is provided with a stepping motor which can easily obtain low speed rotation and high torque instead that it is provided with a small direct current motor which has small torque and a power transmission path with high gear ratio in order to secure high torque that is required to rotate the display portion of the display device which becomes larger and larger. As above described, because the gear ratio of the power transmission path can be lowered and its configuration can be made simple by providing with the stepping motor, the configuration of the rotation driving mechanism also can be made simple. Still further, according to the rotation driving mechanism that is disclosed in JP-A-2004-304679, the stepping motor is utilized and the rotation driving mechanism is structured as a swivel and tilting mechanism which can rotate the display portion of the thin type display device in horizontal direction and in tilt direction respectively.
When the above described rotation driving mechanism is arranged in the thin type display device, if the thin type display device is set up on floor provided with the rotation driving mechanism, and the swivel mechanism portion which makes the display portion rotate in the horizontal direction is driven, vibration is caused in whole device by starting or stopping of the rotating operation because center of gravity of the display portion is high. Especially when the display portion is stopped immediately after the display portion is started to rotate by the swivel mechanism in the horizontal direction, the vibration that is caused in the display portion becomes large. A rotation driving mechanism disclosed in JP-A-H04-061575 employs a structure in that the vibration that is caused by affection of such inertia and the like is prevented mechanically using a leaf spring or the like arranged in a space which is made around upper part of rotating axis. However, there is a limit to perform prevention of the vibration generated in the display portion by such mechanical way.